let sum = (a, b) => a + b;

alert(sum(1, 3));

let double = n => n * 2;

alert(double(3));

let sayHi = () => alert('Hello');

alert(sayHi());

let sum2 = (a, b) => {
    let result = a + b;
    return result;
};

alert(sum2(1, 3));